The technical sector of the invention is that of public works and in particular the building of dams or dykes with embankments of earth-fillings mixed with cement and compacted, normally known as roller-compacted concrete.
One of the problems to be solved with this type of hydraulic structure is that of obtaining a substantially watertight wall upstream, i.e. on the side in contact with the water retained by the structure.
Another problem is to build a substantially watertight wall combined with means permitting a quick draining of the water which has infiltrated behind such wall. It is indeed important, when emptying out the retained water, that no appreciable difference sets up between the level of the restrained water and the level of the water confined behind the wall, as this would create a pressure on that wall which could loosen off the upstream side of the wall of the structure.
It is also important to prevent water from invading the mass of compacted concrete, as this could create uplifts dangerous for the stability of the structure.
It is recalled that structures built in roller-compacted concrete are made up of horizontal layers of earth-fillings mixed with a binder, normally cement, in the proportion of 80 to 150 Kg of cement per m3 of fillings.
Such layers are around 30 cm thick and they are laid and compacted one after the other, with a compaction roller rolling over the layer to be compacted.
The upstream and downstream embankments cannot be roller-compacted and heretofore, various other solutions have been used for treating the faces of such structures, and particularly the upstream face which is required to be substantially watertight and which can be either vertical or inclined.
Methods for constructing a watertight upstream wall are known wherein a wall in conventional reinforced concrete is cast in situ, in successive layers, behind a conventional form or a slip form.
According to some of the conventionally known methods, a layer of earth-fillings mixed with a binder is first deposited, and then compacted, part of the less-compacted earth-fillings constituting the upstream embankment is removed, and a strip of reinforced concrete of the same height as the layer of compacted concrete is cast between a form and said compacted concrete.
According to other conventionally known methods, successive horizontal strips of reinforced concrete are cast, said strips having a height equal to that of two or three layers of earth-fillings and the layers of earth-fillings are deposited one after the other, behind the reinforced concrete wall.
With all these solutions, it is necessary to coordinate the building of the reinforced concrete wall with the laying and compacting of the earth-fillings, which considerably lengthens the works schedule and the non-productive periods.
Another known method consists in constructing a watertight upstream wall composed of prefabricated concrete panels of height equal to that of several layers of earth-fillings, said panels being provided on their internal face with a synthetic moisture barrier and with anchoring members embedded in the mass of compacted concrete, which latter has been deposited and compacted, layer by layer, after positioning of a prefabricated panel.
Yet another known solution consists of placing the binder-enriched earth-fillings behind an upstream form and of adhesively bonding a moisture barrier on the facing after stripping the forms. This solution implies the difficulties of preparing the facing after form stripping and can cause loosening off of the moisture barrier. In addition, said moisture barrier is not protected.